Narrow-bodied, single- and twin-windowed portable laser scanning head for reading bar code symbols

ABSTRACT

A narrow-bodied, single- and twin-windowed, hand-held, laser scanning head for reading bar code symbols includes at least one window mounted at the rear region of the head, and through which either the incident beam going to the symbol and/or the reflected beam returning from the symbol, passes unobstructedly and exteriorly of, and past, the front and intermediate body regions of the head. A field-replaceable laser tube arrangement, a laser tube and method of making the same, an arrangement for and method of controlling a scanning system, optical passive elements for increasing the depth of field, a trigger protective device, and a one-piece support bench and method of fabricating the same by mass-production techniques are also disclosed.

This is a division of application Ser. No. 519,523 filed Aug. 1, 1983now U.S. Pat. No. 4,673,805, which is a division of application Ser. No.342,231 filed on Jan. 25, 1982, now U.S. Pat. No. 4,409,470.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to laser scanning systems forscanning, reading and/or analyzing bar code symbols and, moreparticularly, to a light-weight, easy-to-manipulate,non-arm-and-wrist-fatiguing, hand-held, narrow-bodied, single-andtwin-windowed, laser scanning head supportable entirely by a userthroughout the reading of the symbols. Still more particularly, thisinvention relates to a field-replaceable laser tube arrangement topermit rapid and easy tube replacement; to a novel laser tube and methodof making the same; to an arrangement for, and method of, controlling ascanning system; to optical passive elements for increasing the depth offield; to a trigger protective device; and to a one-piece machinable ormoldable plastic support bench and method of making the same.

2. Description of the Prior Art

Many industries, particularly the grocery and food processing industry,have begun to designate their products with a unique bar code symbolconsisting of a series of lines and spaces of varying widths. Variousbar code readers and laser scanning systems have been developed todecode the symbol pattern to a multiple digit representation forcheck-out and inventory purposes.

Aside from the conventional contact-type and non-contact-type wand orpen bar code readers, true laser scanners, such as point-of-sale or deckscanners of the moving-beam or fixed-beam type, have been built intostationary counters. However, these deck scanners are large, massive,stationary installations. Some symbol-bearing objects are too heavy, ortoo big, or too inconvenient to be brought to the stationary scanninginstallation. Some objects may be stationary themselves.

In order to provide a mobile scanning system, semi-portable laserscanning heads, such as disclosed in U.S. Pat. No. 4,251,798, weredesigned to permit the user to bring the scanning head to the object.However, such semi-portable heads weighed over three pounds, had to bepartially supported by the object itself, and were too heavy andsomewhat difficult to readily manipulate, particularly for thoseassembly-line applications where a user was rountinely required torepetitively manipulate the semi-portable head many times per minute,every hour and on a daily basis.

More modern miniature laser scanners weighing on the order of two andone-half pounds, such as described in U.S. Ser. No. 125,768, filed Feb.29, 1980, entitled "Portable Laser Scanning System and ScanningMethods," and assigned to the same assignee as the present application,now U.S. Pat. No. 4,387,297, have recently been proposed to provide amore truly portable laser scanning head which is supportable entirely bythe user during the reading of the bar code symbols. Although generallysatisfactory for its intended purpose, this fully portable head had arather large case width due to the fact that the laser beam generatedwithin the head was required to be swept over a wide field of viewacross the bar code symbol, which is located in the vicinity of areference place located exteriorly of the housing. The swept laser beam,which was accommodated entirely in the wide-bodied head, therefore,required a great deal of "dead" space within the head. This "dead" spacecaused the case width to be unnecessarily large, and undesirably addedto the overall size and weight of the head, thereby detracting somewhatfrom its features of ease of manipulation and full portability.

Another drawback of the wide-bodied head was that the case widthincreased from the rear towards the front of the head, as considered inthe direction from the housing towards the reference plane, with theresult that the front or nose of the head had a wide snout. In apreferred embodiment, the wide-bodied head had a gun-shapedconfiguration. It was desirable in some applications to insert thegun-shaped head, when not in use, into a user-supported holster of thekind traditionally used to receive and support firearms. However, thewide snout on the wide-bodied head did not lend itself to convenientlyfit in the traditional gun holster. Hence, the wide-bodied heads weretypically tossed and left on the nearest table, and were prone to beingdamaged, misplaced and lost.

Still another drawback associated with the semi-portable and wide-bodiedheads was that any dirt specks on the exit window through which thelaser beam exited en route to the bar code symbol, affected the laserscan at the symbol. The greater the distance between the exit window andthe symbol at the reference plane, the less of a potential malfunctionwould result from dirt specks on the exit window. However, the knownsemi-portable and wide-bodied heads were too dirt-sensitive for someapplications inasmuch as the exit window was too undesirably close tothe reference plane.

Yet another drawback of the prior art laser scanning heads was thatlaser tube replacement generally required skilled personnel usingspecialized equipment. For example, in one technique, the replacementtube was mounted on a bracket which was then positioned by adjustingscrews until the replacement tube was properly aligned with the opticalsystem. This was time- and labor-consuming, and required a skilledtechnician. Another technique involved a mounting bracket on which thetube was prealigned. The bracket and the tube were changed together asan integral assembly. Although this technique allowed replacement byunskilled people, the tube still had to be initially aligned to themounting bracket by a skilled technician. In both techniques, the outputand non-output ends of the used laser tube had to be unsoldered fromtheir respective electrical power wires, and thereupon, the output andnon-output ends of the fresh tube had to be soldered to the respectiveelectrical power wires. This soldering operation was likewise time- andlabor-consuming, and required special tools which might or might nothave been available at a given field installation.

The optical system of a laser scanner head generally used a negativelens at the output end of the laser tube to diverge the collimated laserbeam, and thereupon, used a positive lens to focus the diverging laserbeam to a spot of predetermined diameter at a reference plane locatedexteriorly of the head. The negative lens represented a component ofgiven weight, size and cost, and in the context of a laser scanner headto be made as light-weight, miniature and inexpensive as possible, acomponent which it was desirable to eliminate.

SUMMARY OF THE INVENTION

1. Objects of the Invention

Accordingly, it is the general object of the present invention toovercome the aforementioned drawbacks of the prior art laser scanningheads.

Another object of this invention is to reduce the rather large casewidth heretofore required in prior art wide-bodied laser scanning heads.

Still another object of this invention is to eliminate the amount ofdead space within the head.

Yet another object of this invention is to provide a laser scanning headwhich is so light-in-weight and small-in-volume, that it can be easilyheld in a user's hand without causing arm- and wrist-fatigue, whilebeing easy-to-manipulate, even for those assembly-line applicationswhere the user is routinely required to repetitively manipulate the headmany times per minute, every hour, and on a daily basis.

An additional object of this invention is to provide a fully portablelaser scanning head weighing on the order of one pound.

A further object of this invention is to eliminate the wide snoutheretofore present on prior art wide-bodied laser scanning heads.

Still another object of this invention is to provide a narrow-bodiedlaser scanning head which can readily be received and supported in atraditional V-shaped gun holster, thereby preventing possible damage to,and misplacement and loss of, the head.

Yet another object of this invention is to prevent dirt specks on thelaser exit window of the laser scanning head from adversely affectingthe reading of the bar code symbol.

Another object of this invention is to automatically optically align thelaser tube with the optic system during tube replacement withoutrequiring skilled technicians or specialized equipment to effect thereplacement.

Still another object of this invention is to replace the used laser tubein the head without requiring any desoldering or soldering of anyelectrical power wires.

Yet another object of this invention is to eliminate the negative lensof the optical system, and thereby reduce the overall weight, size andcost of the head.

A further object of this invention is to make the field of view of theincident laser beam traveling towards the symbol and/or the reflectedlaser beam travling back from the symbol substantially independent ofthe case width of the head.

An additional object of this invention is to make the field of view ofthe incident laser beam and/or the reflected laser beam larger than thecase width of the head.

A further object of this invention is to provide a laser scanning headwhich is shock-resistant and resists twisting of the head.

Yet a further object of this invention is to minimize battery powerdrain by actuating all of the actuatable components in the laserscanning head only when they are operative to read and process thesymbol, and by deactuating all of the actuatable components in the headafter the symbol reading and processing has been concluded.

Still a further object of this invention is to independently actuate anddeactuate all of the actuatable components in the laser scanning head byindependently operable means on the head and remote therefrom.

Another object of this invention is to eliminate the electrical powerand communications cable between the laser scanning head and theremainder of the scanning system.

Still another object of this invention is to provide a twin-windowedlaser scanning head combining the advantages of optimum field of viewfor the incident laser beam, optimum field of view for the reflectedlaser beam, low spot speed scanning variation for the laser beam, lowsensitivity to dirt specks on the laser beam exit or scanning window,highlight sensor effectiveness, ease of judging scanning distance to thelight sensor, and minimum case width.

2. Features of the Invention

In keeping with these objects and others will be apparent hereinafter,one feature of the invention resides, briefly stated, in a scanning headof a scanning system for reading bar code symbols. The head ispreferably of light-weight, narrow-bodied, easy-to-manipulate,non-arm-and-wrist fatiguing, and is hand-held and supportable entirelyby a user during symbol reading. The head has an elongated body portionand includes a front region, a rear region, and an intermediate bodyregion extending between the front and rear regions. The head has apredetermined width defined by a pair of opposing side walls spacedtransversely apart of each other. In a preferred embodiment, thehand-held head has a gun-shaped housing, and has a handle portionmounted below the body portion.

The head includes a light source means, e.g. a miniature laser tube or asemiconductor laser diode, mounted within the head, for generating anincident light beam. Optic means, e.g. an optical train consisting of atleast one lens and light-reflecting mirrors, is also mounted within thehead, and is operative for directing the incident beam along a lightpath towards a reference plane located exteriorly of the housing in thevicinity of the front region thereof, and also towards a bar code symbollocated in the vicinity of the reference plane. A reflected light beamis reflected off the symbol, and is directed along a light path awayfrom the reference plane and back towards the housing.

The head further includes scanning means, e.g. a miniature high-speedscanning motor or a miniature mirrored polygon, mounted within the headat the rear region thereof, for sweeping i.e. scanning at least one ofthe beams, i.e. either the incident beam, or the reflected beam, orboth, over a field of view across the bar code symbol. Sensor means,e.g. a pair of miniature photodiodes, is also mounted within the head,for detecting the variable light intensity in the refelcted beam over afield of view across the bar code symbol, and for generating anelectrical analog signal indicative of the detected light intensity.Signal processing means, e.g. analog-to-digital processing circuitry, isalso mounted within the head, for processing the analog signal into adigitized signal to generate therefrom data descriptive of the bar codesymbol.

In accordance with this invention, window means is mounted on thehousing, and in a broad aspect of this invention, a singlelight-transmissive window is mounted at the rear region of the head inclose adjacent confronting relationship with the scanning means thereat.The window is configured and positioned in the light path of the sweptbeam, i.e., either the incident beam, or the reflected beam, or both, topermit the swept beam to pass through the window and unobstructedlytravel exteriorly of and past the front and intermediate body regions ofthe housing.

Due to the exterior transmission of the swept beam outside of the frontand intermediate body regions of the housing, the field of view of theswept beam is substantially independent of the width of the housing. Putanother way, the angular distance through which the incident and/orreflected beams are swept is no longer a function of the width of thehousing. The incident and/or reflected beams can now be swept over anangular distance which is greater than the housing width. Furthermore,the angular distance through which the incident and/or reflected beamsare swept can be maintained at the industrial standard, and the width ofthe housing can be made much narrower in comparison to prior artwide-bodied designs. The amount of dead space within the head has beensignificantly reduced. The overall size and weight of the head islikewise much reduced, thereby further contributing to the fullportability and ease of manipulation features of this invention. Thedesigner of miniaturized laser scanning heads is no longer restricted towide-bodied head configurations.

Similarly, the wide snout at the front of the prior art heads is nolonger a design restraint. The narrow-bodied and streamlined design ofthe head of this invention can readily be received and supported in atraditional V-shaped gun holster, thereby preventing possible damage to,and misplacement and loss of, the head.

In one preferred embodiment, the window at the rear region of the headadjacent the scanning means constitutes a scan window through which theincident beam passes en route to the bar code symbol. Anotherlight-transmissive non-scan window is mounted at the front region of thehead in close adjacent confronting relationship with the sensor meansalso located thereat. The non-scan window is configured and positionedin the light path of the reflected beam to permit the latter to passtherethrough to the sensor means. In this twin-windowed embodiment, thecloseness of the scan window relative to the scanning means maximizesthe field of view of the incident beam; and the closeness of thenon-scan window relative to the sensor means maximizes the field of viewof the reflected beam, and increases the light sensor signal. The scanwindow is advantageously located further from the reference plane andthe front region of the housing as compared to the location of thenon-scan window. This rearward mounting of the scan window helps tominimize the effect of dirt specks on the scan window.

In another twin-windowed embodiment, a reversal of parts causes the rearscan window to be positioned in the light path of the reflected beam,whereas the front non-scan window is positioned in the light path of theincident beam. In this embodiment, the light source is mounted at thefront of the head in close adjacent confronting relationship with thenon-scan window located thereat. The scanning means remains at the rearof the head adjacent the scan window. In operation, the light sourceilluminates the symbol, and the reflected beam travels unobstructedlyand exteriorly of and past the front and intermediate body regions ofthe head. The scanning means sweeps the reflected beam and, in turn,directs the swept beam to the sensor means for further processing.

In still another preferred embodiment, only a single window is mountedat the rear of the head in close adjacent confronting relationship withthe scanning means thereat. The single window is configured andpositioned in the light paths of both the swept incident and reflectedbeams to permit both beams to pass through the window and unobstructedlytravel exteriorly of and past the front and intermediate body regions ofthe head. this retro-reflective scanning is advantageous in someapplications, because it eliminates the need for the second window, asdescribed in the earlier twin-windowed embodiments.

Yet another feature of this invention resides in a field-replaceablelaser tube arrangement which automatically optically aligns the lasertube with the optic system of the head during tube replacement withoutrequiring skilled technicians or specialized equipment to effect thereplacement, and without requiring any desoldering or soldering of anyelectrical power wires.

An additional feature of this invention resides in eliminating thenegative lens of the optical system by modifying the laser tube of thehead to have a diverging output laser beam. In prior art designs, theoutput beam of the laser tube was collimated, i.e. had a substantiallyflat wavefront. It was necessary therefore to use a negative lens todiverge the collimated laser beam, and thereupon, to use a positive lensto focus the diverging laser beam to a circular spot of predetermineddiameter at the reference plane. However, by modifying the laser tube tohave a diverging output beam, the negative lens and its attendantweight, size, space requirements and cost aspects are eliminated,thereby contributing to the overall portability of the head.

Still other features relate to increasing the depth of field by usingoptical passive elements rather than electronic circuitry, minimizingbattery drain by actuating the components in the head only when thesymbol is being read, and fabricating an optical support bench bymass-production techniques.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a gun-shaped, narrow-bodied,twin-windowed embodiment of a laser tube-based portable laser scanninghead in accordance with this invention;

FIG. 2 is a partially broken-away, top sectional view of the embodimentof FIG. 1;

FIG. 3 is a rear sectional view as taken along line 3--3 of FIG. 1;

FIG. 4 is a top plan sectional view of a detail of the embodiment ofFIG. 1, showing the laser tube and part of the optical train;

FIG. 5 is a front elevational view of the embodiment of FIG. 1;

FIG. 6 is a front perspective view of the FIG. 1 embodiment, on a muchsmaller scale, and diagrammatically shows the interconnection of thehead to the remainder of the scanning system;

FIG. 7A is a top plan schematic view of a prior art wide-bodied head;

FIG. 7B is a top plan schematic view of an alternate, but unacceptable,design of a laser scanning head;

FIG. 7C is a top plan schematic view of another alternate, butunacceptable, design of a laser scanning head;

FIG. 7D is a top plan schematic view of the laser scanning head of FIG.1;

FIG. 8 is a side sectional view of a gun-shaped, narrow-bodied,twin-windowed embodiment of a laser diode-based portable laser scanninghead in accordance with this invention;

FIG. 9 is a partially sectioned, top plan view of the embodiment of FIG.8;

FIG. 10 is a side schematic view of a gun-shaped, narrow-bodied,twin-windowed embodiment of a light-based portable scanning head inaccordance with this invention;

FIG. 11 is a top plan schematic view of the embodiment of FIG. 10;

FIG. 12 is a side schematic view of a gun-shaped, narrow-bodied,single-windowed, retro-reflective embodiment of a light-based scanninghead in accordance with this invention;

FIG. 13 is a top plan schematic view of the embodiment of FIG. 12;

FIG. 14 is a partially schematic, rear elevational view of thecomponents mounted in the rear region of the FIG. 12 embodiment;

FIG. 15 is a field-replaceable laser tube arrangement for use in any ofthe aforementioned laser tube-based embodiments;

FIG. 16 is a partially schematic, partially sectional, side view of anovel laser tube having a diverging output laser beam made in accordancewith one method of this invention; and

FIG. 17 is a partially schematic, partially sectional, side view of anovel laser tube having a diverging output laser beam made in accordancewith another method of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-6 of the drawings, reference numeral 10generally identifies a light-weight, narrow-bodied, streamlined,narrow-snouted, hand-held, fully portable, easy-to-manipulate,non-arm-and-wrist-fatiguing, twin-windowed laser scanning headsupportable entirely by a user for use in a laser scanning systemoperative for reading, scanning and/or analyzing bar code symbolsthroughout the reading thereof. Such symbols comprise a series of linesand spaces of varying widths, which pattern decodes to a multiple-digitrepresentation characteristic of the product bearing the symbol. Typicalsymbol bar codes in current use are the Universal Product Code (UPC),EAN, Codabar and Code 39.

Turning now to FIG. 1, the head 10 includes a generally gun-shapedhousing having a handle portion 12 and an elongated, narrow-bodiedbarrel or body portion 14. The handle portion 12 has a cross-sectionaldimension and overall size such that it can conveniently fit in the palmof a user's hand. Both the body and handle portions are constituted of alight-weight, resilient, shock-resistant, self-supporting material, suchas a synthetic plastic material. The plastic housing is preferablyinjection-molded, but can be vacuum-formed or blow-molded to form a thinshell which is hollow and bounds an interior space whose volume measuresless than a value which is on the order of 50 cubic inches. The specificvalue of 50 cubic inches is not intended to be self-limiting, but hasbeen provided merely to give an approximation of the overall maximumvolume and size of the head 10. The overall volume can be less than 50cubic inches and, indeed, in some applications, the volume is on theorder of 25 cubic inches.

The body portion 14 is generally horizontally elongated along alongitudinal axis, and has a front region 16 at the front end, a raisedrear region 18 at the rear end, and an intermediate body region 20extending between the front and rear regions. The body portion 14 has atop wall 11 above which the raised rear region 18 projects, a bottomwall 13 below the top wall, a pair of opposed side walls 15, 17 spacedtransversely apart of each other by a predetermined width dimension, afront wall or nose 19, and a rear wall 21 spaced rearwardly of the frontwall.

A light source means, i.e., laser tube 22 having an anode or output end23 (see FIG. 4) and a cathode or non-output end 25, is mounted withinthe body portion 14 lengthwise along the longitudinal axis, and isoperative for generating an incident collimated laser beam. An opticmeans, i.e., an optical train, is likewise mounted within the bodyportion, and is operative for directing the incident beam along a lightpath towards a reference plane located exteriorly of the housing in thevicinity of the front region 16, as shown in FIGS. 1 and 2. A bar codesymbol to be read is located in the vicinity of the reference plane,that is, anywhere within the depth of focus of the incident beam asdescribed below, and the light reflected from the symbol constitutes areflected laser beam which is directed along a light path away from thereference plane and back towards the housing.

As best shown in FIGS. 4 and 5, the optic train includes an opticalbench 24, a negative or concave lens 26 which is fixedly mounted in acylindrical bore 25 of the bench, a light-reflecting mirror 26' which isfixedly mounted on an inclined surface 27 of the bench, anotherlight-reflecting mirror 28 which is fixedly mounted on another inclinedsurface 29 of the bench, a positive or convex lens 30 which isadjustably mounted on the bench by means of a set screw 31, and stillanother light-reflecting mirror 32 which is adjustably mounted on abendable metal bracket 33.

The optical bench 24 has an enlarged cylindrical recess 35 whichcommunicates with the smaller bore 25. The laser tube 22 is snuglyreceived in a cylindrical support sleeve 34 which, in turn, is snuglyreceived in the bore 25. An electrically conductive element or washer 36is located at the shoulder between the recess 35 and bore 25. The washer36 makes an electro-mechanical, non-soldered contact with the output end23 of the tube. Another electrically conductive element, preferably aresilient wire 38, is mounted at the non-output end 25 of the tube. Thewire 38 has one coiled end looped around the non-output end 25, anintermediate taut wire portion extending lengthwise of the tube, and itsother end is fixedly secured to the bench 24 by the set screw 37. Thewire 38 is preferably made of a resilient, spring-like material, and itstautness functions much like a spring or biasing means for affirmativelyurging the output end 23 into affirmative, electro-mechanical contactwith the washer 36. The non-output end 25 is grounded via the wire 38;and a high voltage power wire (not shown) from the power supplycomponent 40 mounted in the handle portion 12 is electrically connectedto a ballast resistor 42 mounted in another bore formed in the bench 24.The ballast resistor is, in turn, electrically connected to the washer36 by a wire, not illustrated for the sake of clarity. It will be notedthat neither the output nor non-output end of the tube is directlysoldered to any electrical wire, a feature which is highly desirable ineffecting on-site tube replacement. The bore 25 and recess 35 aremechanically bore-sighted so that the laser output beam is automaticallyoptically aligned with the optic train when the sleeve-supported tubeand output end are fully inserted into the recess 35 and bore 25,respectively.

The bench 24 is a one-piece light-weight part machined or preferablymolded by inexpensive mass-production techniques of a dimensionallystable, flame-retardant material, such as Delrin (Trademark), orglass-filled Noryl (Trademark), preferably having a high dielectricbreakdown (on the order of 500 volts/mil). In order to take into accountthe slight variations in beam alignment which unavoidably result fromdifferent tubes and from tolerance variations in the tube itself, thebore 25, and the recess 35, the very weak negative lens 26 (on the orderof -24mm) is mounted very close to the output end of the tube, and allthe elements in the optical path are made large enough to allow the beamto pass unobstructedly even if the beam is not exactly on center. Theclose mounting of the weak lens 26, and the short optical path (about38mm) between lenses 26 and 30, mean that the optical tolerances in theremainder of the beam path can still be off by about 1/2° withoutsacrificing system performance. This provides the advantage that thebench can be

Thus, the beam emitted from the output end 23 first passes through thenegative lens 26 which functions to diverge the initially collimatedbeam. Then, the divergent beam impinges the mirror 26', and is thereuponreflected laterally to impinge the mirror 28, whereupon the beam isreflected upwardly to pass through the positive lens 30 which isoperative to converge the divergent beam to a generally circular spot ofapproximately an 8 mil to 10 mil diameter at the reference plane. Thespot size remains approximately constant throughout the depth of focusat either side of the reference plane. The converging beam from the lens30 impinges on the adjustable mirror 32, and is thereupon laterallyreflected to a scanning mirror 44 which forms part of the scanningmeans.

The scanning means is preferably a high-speed scanner motor 46 of thetype shown and described in co-pending U.S. application Ser. No.125,768, filed Feb. 29, 1980, entitled "Portable Laser Scanning Systemand Scanning Methods," and assigned to the same assignee as the presentapplication. The entire contents of said application are incorporatedherein by reference, now U.S. Pat. No. 4,387,297, and made part of thisapplication. For purposes of this patent, it is sufficient to point outthat the scanner motor 46 has an output shaft 41 on which a supportplate 43 is fixedly mounted. The scanning miror 44 is fixedly mounted onthe plate 43. The motor 46 is driven to reciprocally and repetitivelyoscillate the shaft in alternate circumferential directions over arclengths of any desired size, typically less than 360°, and at a rate ofspeed on the order of a plurality of oscillations per second. In apreferred embodiment of this invention, the scanning mirror 44 and theshaft are jointly oscillated so that the scanning mirror repetitivelysweeps the beam impinging thereon through an angular distance A or anarc length of about 25° and at a rate of about 40 oscillations persecond.

Stop means, i.e., an abutment 48, is fixedly mounted on a bracket 49which is, in turn, mounted on the bench 24. The abutment 48 is locatedin the path of oscillating movement of the plate 43 for the scanningmirror 44, for preventing the mirror from making a complete 360°rotation during shipping. The abutment never strikes the mirror duringscanning; the abutment serves to keep the mirror properly aligned, thatis, always facing towards the front of the head.

The scanning motor 46 is mounted on the bench 24 slightly offset fromthe longitudinal axis. Other miniature scanning elements can beutilized. For example, miniature polygons driven by motors can be used,or the various bimorph scanning oscillating elements described in U.S.Pat. No. 4,251,798 can be used, or the penta-bimorph element describedin U.S. Pat. No. 4,387,297 can be used, or the miniature polygon elementdescribed in co-pending U.S. application Ser. No. 133,945, filed Mar.25, 1980, entitled "Portable Stand-Alone Desk-Top Laser ScanningWorkstation For Intelligent Data Acquisition Terminal and Method ofScanning," now U.S. Pat. No. 4,369,361 and assigned to the same assigneeas the present application, the entire contents of which are herebyincorporated herein by reference and made part of this disclosure, canbe used.

Although only a single scanner element is shown in the drawings forcyclically sweeping the laser beam across the symbol along apredetermined direction (X-axis scanning) lengthwise thereof, it will beunderstood that another scanner element may be mounted in the head forsweeping the symbol along a transverse direction (Y-axis scanning) whichis substantially orthogonal to the predetermined direction. In someapplications, multiple line scanning is preferred.

Referring again to FIGS. 1 and 2, the scanning mirror 44 is mounted inthe light path of the incident beam at the rear region 18 of the head,and the motor 46 is operative for cyclically sweeping the incident beamthrough an angular distance A over a field of view across the bar codesymbol located in the vicinity of the reference plane. A laserlight-transmissive scan window 50 is mounted on the raised rear region18, behind an opening 51 formed therein in close adjacent confrontingrelationship with the scanning mirror 44 thereat. As used throughout thespecification and claims herein, the term "close adjacent confronting"relationship between components is defined to mean that one component isproximally located relative to the other component, typically less thanone inch apart of each other. As shown in FIG. 1, the scan window 50 isconfigured and positioned in the light path of the incident beam topermit the latter coming from the scanning mirror 44 to travel adistance of less than one inch within the raised rear region 18, andthen to pass through the scan window 50, and thereupon to travelunobstructedly and exteriorly of and past the intermediate body region20 and the front region 16 of the housing, and then to impinge on thesymbol located at or near the reference plane.

The closer the scanning mirror 44 is to the scan window 50, the largerwill be the field of view of the swept incident beam for a given scanangle. It will be noted that the width dimension of the scan windowrepresents a limiting factor for the sweep of the incident beam, becausethe housing walls bounding the scan window would clip and block any beamwhich was swept beyond the width of the scan window. Hence, as a rule,the scanning mirror is made as close as possible to the scan window tooptimize the field of view of the swept incident beam.

As best shown in FIG. 2, the field of view of the swept incident beam issubstantially independent of the width of the body portion 14 and, infact, the field of view, i.e., the transverse beam sweep dimension, ofthe swept incident beam is actually larger than the width of the bodyportion 14 at the front region 16 and at the forward section of theintermediate body region 20. This is, of course, enabled by the factthat the swept incident beam has been transmitted outside of the frontand intermediate body regions of the housing. The side walls 15, 17 arenot in the light path and do not clip or block the swept incident beam.The scan window 50 is mounted on the rear region 18 at an elevationabove the top wall 11 to permit an overhead unobstructed transmission.

In a preferred embodiment, the width of the body portion 14 is on theorder of 13/4 inches, whereas the width of the field of view at thereference plane is on the order of 31/2 inches. In prior art wide-bodieddesigns, the width of the housing was greater than 31/2 inches in orderto obtain a 31/2 inch width of the field of view for a given scan angle.Hence, the exterior transmission of the swept incident beam permits thehead of the present invention to have a narrow-bodied streamlinedconfiguration. The side walls 15, 17 need no longer diverge outwardlytowards the front as in prior art designs to accommodate the swept beam,but can be made substantially parallel as shown, or in any other shapeas desired.

In a preferred embodiment, the reference plane is located about 2 inchesfrom the front wall 19 of the head, and is located a linear distance ofabout 91/2 inches from the positive lens 30. The depth of field at thereference plane is about 23/4"on either side of the reference plane.These numerical figures are not intended to be self-limiting, but aremerely exemplary.

A laser light-transmissive non-scan window 52 is mounted on the frontwall 19 in close adjacent confronting relationship with the sensor means54 located at the front region 16. The sensor means 54 is operative fordetecting the intensity of the light in the reflected beam coming fromthe symbol over a field of view across the same, and for generating anelectrical analog signal indicative of the detected light intensity. Inorder to increase the zone of coverage of the sensor means, a pair ofsensor elements or photodiodes 54a, 54b are located on opposite sides ofthe longitudinal axis. The sensor elements lie in intersecting planesand face both forwardly and laterally. The front wall 19 is likewiseconstituted of a pair of tapered wall portions 19a, 19b, each of whichhas an opening 53a, 53b formed therein. A pair of non-scan windowportions 52a, 52b is fixedly mounted behind the openings 52a, 52b,respectively. Each non-scan window portion is mounted in close adjacentconfronting relationship with its respective sensor element. Thenon-scan window portions are configured and positioned in the light pathof the reflected beam to permit the latter to pass therethrough to thesensor elements. Two small non-scan window portions are preferablyutilized, rather than a single non-scan window, because two smallerwindows are inherently stronger than one due to the greater perimeterthat two windows provide.

The scan window 50 is located rearwardly of the non-scan window 52. Eachwindow 50, 52 is located at a different distance from the referenceplane and the front wall 19. The scan window 50 is elevated above thenon-scan window 52, as described above. The non-scan window portions arelocated at opposite sides of the longitudinal axis. The scan window islocated on the longitudinal axis.

A printed circuit board 59 is mounted within the body portion 14, andvarious electrical sub-circuits diagrammatically represented byreference numerals 55, 56, 57, 58 are provided on the board 59. Signalprocessing means 55 is operative to process the analog signal generatedby the sensor element to a digitized signal to generate therefrom datadescriptive of the bar code symbol. Suitable signal processing means forthis purpose was described in U.S. Pat. No. 4,251,798. Sub-circuit 56constitutes drive circuitry for the scanner motor 46. Suitable motordrive circuitry for this purpose was described in U.S. Pat. No.4,387,297. Sub-circuits 57 and 58 constitute a safety circuit for thelaser tube, and voltage regulator circuitry. Suitable circuitry for thispurpose were also described in U.S. Pat. No. 4,387,297.

Shock mounting means are mounted at the front and rear regions of thebody portion, for shock mounting the laser, optical and scanningcomponents within the body portions. An annular shock collar 60,preferably of rubber material, surrounds the forward end of the tube 22and engages the bottom wall 13 and the underside of the circuit board59. Board support elements 61a, 61b extend downwardly of the top wall 11to rigidly support the circuit board 59. A pair of rubber shock mounts62, 64 are fixedly mounted on opposite sides of the optical bench 24,and respectively engage the side walls 15, 17 at the rear region 18 ofthe housing. The shock mounts 62, 64 and the collar 60 are spacedlongitudinally apart of each other and engage the thin-walled housing atthree spaced locations to isolate twisting of the housing from thelaser, optical and scanning components.

Electrical power is supplied to the laser tube 22 by the power supplycomponent 40 mounted within the handle portion 12. The power supplycomponent which steps up a 12vDC battery voltage to over 1 kilovolt isthe heaviest component in the head, and its mounting in the handleportion allows for a low center of gravity and for better balance of thehead.

A non-bulky, collapsible, coil-type cable 66 (see FIG. 6) electricallyconnects the head 10 to the remainder of the scanning system, whichincludes a battery-powered decode module 68 and a host computer 70. Thecoil-type cable 66 is readily flexible and permits user manipulation ofthe head 10 with multiple freedoms of movement from one symbol to thenext without requiring excessive strength by the user. The cable 66includes a plurality of conductive wires which are all relatively thinand flexible. For example, one wire carries the 12vDC low voltage signalfrom the battery in the decode module 68 to the power component 40.Another wire carries the digitized signal from the analog-to-digitalsignal processing circuitry 55 to the decode module 68 for decodingpurposes. This latter wire is non-radio-frequency-shielded, and hence,is readily flexible. The remaining wires carry low voltage control andcommunication signals. All of the wires of the cable 66 are connectedtogether to a common plug-type connector 72. A mating connector 74 ismounted within the head, and receives the connector 72 in a matingrelationship. The use of the mating connectors 72, 74 permits rapidreplacement of the cable for on-site repairs. The electrical connectionsbetween the connector 74 and the various components in the head havebeen omitted from the drawings for the sake of clarity.

The decode module 68 processes the digitized signal generated in thehead, and calculates the desired data, e.g. the multiple digitrepresentation or code of the bar code symbol, in accordance with analgorithm contained in a software program. The decode module 68 includesa PROM for holding the control program, a RAM for temporary datastorage, and a microprocessor which controls the PROM and RAM and doesthe desired calculations. The decode module also includes controlcircuitry for controlling the actuatable components in the head asdescribed below, as well as two-way communications circuitry forcommunicating with the head and/or with the host computer 70. The hostcomputer 70 is essentially a large data base, and provides informationfor the decoded symbol. For example, the host computer can provideretail price information corresponding to the decoded symbols.

A manually-actuatable trigger switch 76 is mounted on the head in theregion where the handle portion 12 is joined to the body portion 14.Depression of the trigger switch 76 is operative to turn themicroprocessor in the decode module on. Upon release of the triggerswitch, the spring 78 restores the switch to its initial position, andthe microprocessor is turned off. In turn, the microprocessor iselectrically connected to the actuatable components in the head via thecable 66 to actuate and deactuate the actuatable components when themicroprocessor is respectively turned on or off by the trigger switch.

In prior art heads, the trigger switch was only operative to turn thelaser tube and/or scanner motor on or off. Now, the trigger switch turnsthe microprocessor on or off and, in turn, all of the actuatablecomponents in the head on or off. The microprocessor is a large powerdrain on the battery built into the decode module. Hence, by controllingthe on-time of the microprocessor to only those times when a symbol isbeing read, that is, when the trigger switch is depressed, the powerdrain is substantially reduced, and the battery life substantiallyincreased (over 5 hours).

Another feature of this invention is embodied in turning themicroprocessor on or off by means of the host computer 70 which isremote from the head 10. The computer 70 typically includes a keyboardand a display. Once a user makes an entry on the keyboard for example,by entering the identity of the code to be decoded, the computerrequests the microprocessor to turn itself on, store the information,and then to turn the microprocessor off. The microprocessor, again, ison only for so long as is necessary to comply with the computer request.The trigger switch and the keyboard computer entry are independentlyoperable means for directly controlling the microprocessor, and forindirectly controlling the actuatable components in the head.

Another useful feature in having the microprocessor, rather than thetrigger switch, directly control the laser tube is to keep an accuraterecord of laser on-time for governmental recordkeeping. It is, ofcourse, far easier to keep track of laser on-time in the software of amicroprocessor than to manually record the laser on-time.

A set of visual indicators or lamps 80, 82, 84 is also mounted on thecircuit board 59, each lamp being positioned below a correspondingopening in the top wall 11. The lamps are operative to visually indicateto the user the status of the scanning system. For example, lamp 80illuminates whenever the laser tube is energized, thereby continuouslyadvising the user whether the tube is on or off. Lamp 82 illuminateswhen a successful decode has been obtained. It will be recalled that theincident beam is swept over a symbol at a rate of about 40 scans persecond. The reflected beam may be successfully decoded on the firstscan, or on any of the successive scans. Whenever a successful scan hasbeen obtained, the microprocessor will cause the lamp 82 to beilluminated to advise the user that the head is ready to read anothersymbol.

It is believed that the operation of the scanning system is self-evidentfrom the foregoing, but by way of brief review, the gun-shaped head isgrasped by its handle portion, and its barrel is aimed at the bar codesymbol to be read. The sighting of the symbol is facilitated by the factthat the barrel is narrow-bodied, and that there are no obstructions onthe front and intermediate body regions of the barrel. The front wall ofthe barrel is situated close to the symbol, it being understood that thesymbol can be located anywhere in the depth of field at either side ofthe reference plane.

The trigger switch is then depressed, thereby causing the microprocessorto energize the laser tube, the scanner motor, the sensor elements, andall the electronic circuitry provided on the printed circuit board. Thelaser tube emits a beam, which is then routed through the optic train asdescribed above, and thereupon, the scanning mirror reflects the beamthrough the scan window and out of the head exteriorly of and past thefront and intermediate body regions of the body portion of the head. Thereflected beam passes through the non-scan window portions to the sensorelements and is subsequently processed by the signal processingcircuitry. The processed signal is conducted to the decode module fordecoding. Once a successful decode has been realized, the microprocessorilluminates the lamp 82 and deactuates the head, and the user is nowadvised that the head is ready to be aimed at another symbol. Theflexibility of the coil-type cable faciliates the movement of the headto the next symbol.

In addition, the movement of the head from one symbol to the next isfacilitated by the relatively low weight of the head. The head with allthe aforementioned components therein weighs less than one pound. Thisrepresents a significant breakthrough in the art of miniaturized andportable laser scanning heads.

The twin-windowed head (the pair of non-scan window portions 52a, 52bconstitutes one non-scan window 52; the scan window 50 constitutes theother window) with the rear, raised scan window 50 overcomes severalproblems associated with the prior art heads. To facilitate theexplanation of these problems and how the twin-windowed head of thisinvention solves these problems, the top plan schematic views of FIGS.7A, 7B, 7C, 7D have been provided. FIG. 7A diagrammatically illustratesa prior art wide-bodied head of the type shown in the aforementionedco-pending application U.S. Ser. No. 125,768, now U.S. Pat. No.4,387,297. FIGS. 7B and 7C diagrammatically illustrate some head designalternatives, but which are unacceptable, because they fail to solve allof the prior art problems. FIG. 7D diagrammatically illustrates thenarrow-bodied, twin-windowed head of the present invention, aspreviously described in FIGS. 1-6.

FIG. 7A shows an elongated body portion or barrel 86 having a rearscanning means 44, 46, as described above, operative to sweep anincident beam through a scan angle A of predetermined arc length, e.g.,25°, through a single front window 92. The reflected beam also passesthrough the front window 92 to be detected by the sensor elements 54a,54b, also described above. The barrel is relatively wide-bodied toaccommodate the swept incident beam within the barrel, and the front ofthe housing is relatively close to the reference plane.

As compared to FIG. 7A, FIG. 7B shows a narrower barrel 88 having a moreforwardly scanning means 44, 46 operative for sweeping the incident beamthrough a larger scan angle B, e.g. on the order of 45°, through asingle front window 94. The reflected beam also passes through the frontwindow to be detected by the sensor elements 54a, 54b. The front of thehousing is spaced further from the reference plane.

As compared to FIG. 7B, the scanning means 44, 46 in FIG. 7C is locatednear the middle of the barrel 90, and is operative to sweep the incidentbean through the original 25° scan angle through the single front window96. The reflected beam also passes through the front window fordetection by the sensor elements 54a, 54b. The front of the housing isspaced much further from the reference plane.

FIG. 7D needs no detailed description, except to repeat that the rearscanning means 44, 46 has its scan window 50 rearwardly located on thehousing. The scan window 50 is raised so that the swept incident beam isnot accommodated within the barrel 14. The reflected beam passes througha different window, i.e., the non-scan window 52 located at the front ofthe barrel.

In rating the performance of a laser scanning head, the spot speedvariation of the scan across the symbol should ideally be constant sothat the signal processing circuitry can be simple, i.e., withoutrequiring sophisticated circuitry to compensate for the spot speedvariation. By way of example, the spot speed at point X in the depth offield C is much greater than the spot speed at point Y. It is well knownthat the lower the scan angle A, the lower will be the projected spotspeed variation. Hence, a 25° scan angle as illustrated in FIGS. 7A, 7C,7D is better in terms of spot speed variation than the 45° scan angle ofFIG. 7B.

As noted above, the problem of dirt specks on the scan or exit windowadversely affects the scanning ability, particularly where the window ispositioned in the light path where the scan spot is focused andrelatively small. Hence, the greater the spot size and concomitantly thegreater the distance between the exit window and the reference plane,the better the scanning performance. Hence, the head of FIG. 7D with itsrear exit window 50 the furthest from the reference plane has the leastsensitivity to dirt specks, and the heads of FIGS. 7C, 7B, 7A aresuccessively more sensitive to dirt specks.

In terms of light sensor effectiveness, the closer the sensor elementsare to the reference plane, the more sensitive will be the detection bythe sensor elements. Hence, the heads of FIGS. 7D and 7A have the bestlight sensitivity; the head of FIG. 7B has less light sensitivity; andthe head of FIG. 7C has the worst light sensitivity.

In operation, it is easier for a user to gauge a working distance closeto the head, rather than a working distance located far therefrom.Typically, it is easier for the user to aim the head at a symbollocated, for example, anywhere between 1/4" and 6" away from the frontwall of the barrel, rather than aim the head at a symbol located, forexample, between 9" and 12" from the front wall. Hence, the heads ofFIGS. 7D and 7A are the best in terms of user convenience; the head ofFIG. 7B is less convenient; and the head of FIG. 7C is the mostinconvenient.

Of great importance is the effect that the barrel width has on the widthof the scan. As shown in FIG. 7A, the entire width of the scan must beaccommodated in the barrel 86, thereby resulting in a wide-bodied,unaesthetic design. If the scanner means is moved forwardly as shown inFIG. 7B so as to narrow the width of the barrel, then the scan anglemust be increased to obtain the same field of view. As noted above,increasing the scan angle is not an acceptable solution, because itworsens the spot speed variation performance. If the scanner means ismoved rearwardly back towards the middle of the barrel, and the scanangle is kept at its original arc length, and the body is kept narrow,as shown in FIG. 7C, then the light sensor effectiveness will worsen,and the convenient judgment of scan distance will worsen.

In a non-retro-reflective mode, the applicants have recognized that theuse of a single front window through which the incident and reflectedbeams must pass has conflicting requirements. By providing a rear windowand a front window for the beams, these conflicting requirements areresolved. The head of FIG. 7D has the best insensitivity to dirt speckson the exit window, as the narrowest barrel width, and has optimumcontrol over spot speed variation, optimum ease of judging scandistance, and optimum light sensor effectiveness.

In accordance with the invention, the housing need only be large enoughto accommodate the components. This benefits styling, cost and weight.The scan width may be varied from one application to the next withoutmaking a change in the barrel. By mounting the scanning means close tothe rear scan window, the field of view of the incident beam is madevery wide. Analogously, by mounting the sensor means close to the frontnon-scan window, the field of view of the reflected beam is made verywide. Furthermore, the close mounting of the scanning and sensor meansto their respective windows, eliminates the prior art narrow slitaperture, and eases optical alignment of the incident beam, and avoidspotential clipping of the incident beam if the beam angle drifts.

Referring now to FIGS. 8 and 9, the gun-shaped head 100 is essentiallyanalogous to the head 10, except as noted below. Hence, any likecomponents in FIGS. 8 and 9 have been identified with the same referencenumerals as were used previously. Rather than a laser tube, asemiconductor laser diode 102 is mounted within the barrel 14 togenerate an incident laser beam. Rather than a folded path opticaltrain, an optics tube 104 is axially aligned with the laser diode. Alight-reflecting mirror 106 is adjustably mounted on a bendable bracket108 that is mounted on the exterior of the tube 104. The mirror 106 ispositioned in the light path of the incident beam to direct the incidentbeam towards the scanning mirror 44 of the scanner motor 46. Asdescribed previously, the motor 46 is operative to sweep the incidentbeam through the rear scan window 50 and outside of the barrel 14 pastthe intermediate body region 20 and front region 16 thereof. Thereflected beam passes through the non-scan window 52 to the sensor means54 for detection and subsequent processing as previously described.

A keyboard 110 and a display 112 are mounted on the top wall 11 of thebarrel. The keyboard 110 comprises a plurality of manually-depressablekeys, each for a different numeral, and a set of function keys tocalculate and display various functions required in a given application.The display 112 may be of the low power LCD type. By mounting thedisplay 112 and the keyboard 110 on the head 100, this featurefacilitates keyboard entry and data reading at the site of the symbol tobe read, rather than at a more remote location away from the head.

Inasmuch as the laser diode 102 does not require a voltage step-upcomponent 40, but can be energized directly from a low voltage battery,a battery 114 is mounted within the handle 12 to energize the diode. Inorder to even further facilitate the movement of the head 100 relativeto the remainder of the system, the aforementioned cable 66 is totallyeliminated. In its place, a transmitting antenna 116 may be mounted atthe rear of the handle, and is operative to electromagnetically transmitthe processed information to the remainder of the system. In addition tocircuit board 59, another circuit board 118 is provided within thebarrel to accommodate the additional electronic circuitry for thekeyboard and the display.

Still another circuit board 120 is mounted within the barrel toaccommodate a radio transmitter 124 and a frequency shift key modulator125. The modulator 125 will place one or another tone (frequency) on theradio wave generated by the transmitter 124 and telemetered over theantenna 116. In one embodiment of the invention, the telemetered signalcorresponds to the digitized signal generated in the head, and thetelemetered signal is received by a receiver and a demodulator, whichare incorporated in the decode module 68. In this case, the decodemodule 68 must also have a return transmitter and a modulator forelectromagnetically telemetering the decoded information back to thehead 100, where the decoded information is then received and demodulatedby a return receiver 126 and a demodulator 127, which are also mountedon circuit board 120. The decoded information can be displayed ondisplay 112.

In another embodiment of the invention, the entire decode module 68 maybe reduced by large scale integration to one or two integrated circuitchips, e.g. chips 128, 129, which are mounted on yet another printedcircuit board 122 provided in the barrel. In this case, the digitizedsignal generated by sub-circuit 55 is decoded by chips 128, 129 right inthe head 100, rather than at some location remote from the head. Hence,the telemetered signal corresponds to the decoded signal generated inthe head, and the telemetered signal is transmitted not to a remotedecode module, but directly to the host computer 70, which must nowinclude a receiver and a demodulator for the decoded signal. Of course,the host computer must also include a return transmitter and a modulatorfor electromagnetically telemetering the desired data back to the head100, where the data is then received and demodulated by the returnreceiver 126 and the demodulator 127. The data can be displayed ondisplay 112.

The laser scanning head 100 shown in FIGS. 8 and 9 constitutes acomplete and independent data processing workstation in the sense thatit is fully portable; it is battery-powered; it decodes the symbol inthe head; and it is not mechanically connected to any remote systemcomponent. The head 100 is readily adaptable to interact with any hostcomputer.

As noted previously, the host computer or terminal 70 is a data base,and may be incorporated in a built-in large computer installation; orcan be made smaller and constitute a light-weight, hand-held, discreteunit; or, as shown in FIGS. 8 and 9, can constitute an integratedcircuit storage chip 129' and be mounted within the head 100 on board122 to form a complete data collection terminal which facilitatesreal-time and subsequent data processing at the site of the symbol to beread. As described above, the interconnection between the module 68 andcomputer 70 can be hand-wired, or by means of telemetry, or by plug-inconnection, or by electrical circuit connection in the head.

Referring now to FIGS. 10 and 11, reference numeral 130 generallyidentifies a gun-shaped, laserless, twin-windowed head analogous to theprevious heads 10, 100, except as noted below. To simplify thedescription of head 130, like parts previously described in connectionwith the earlier embodiments have been identified with like referencenumerals. One major distinction of the head 130 is that the incidentbeam is not swept, but is transmitted from the front of the housing, andthat it is the reflected beam that is swept over its field of view. Putanother way, the sensor means sweeps across the symbol. It is thereflected beam that unobstructedly travels exteriorly of and past thefront and intermediate body regions of the housing.

Rather than a laser tube or laser diode, the laserless head 130comprises a light source 132 which includes a pair of light sourceelements 132a, 132b at opposite sides of the longitudinal axis, eachlight source element facing both forwardly, upwardly and laterally toemit a light beam. Again, the light source elements need not generate alaser beam but are operative to generate any type of light beam, and mayconstitute high-powered LED's (30-100mW) or a miniature quartz halogenbulb. The incident light beam passes through a light-transmissive frontnon-scan window 152 located at the front region 16 of the body portion20 of the head in close adjacent confronting relationship with the lightsource elements 132a, 132b thereat. In a variant from non-scan window52, the non-scan window 152 is a wrap-around window which extendstransversely along the front wall and also partially along the sidewalls of the head. After passing through the non-scan window 152, theincident beam illuminates the symbol. It is preferable if the incidentbeam is directed slightly upwardly, such that the reflected beam will bedirected, as shown, that is, exteriorly of and past the front region 16and intermediate body region 20 above the top wall of the body portion.The reflected beam passes through the raised rear scan window 150 andimpinges on the scanning mirror 44 which is being repetitivelyoscillated by the scanner motor 46 to scan the field of view of thereflected beam across the symbol. The swept reflected beam is thereupondirected towards the light-reflecting mirror 134 which is adjustablymounted on a bendable mounting bracket 136 on a sensor optic tube 138.The mirror 134 is positioned in the light path of the reflected beam todirect the reflected light off the mirror 44 through the sensor opticstube 138 to the sensor means 140 mounted within the body portion 14 atthe rear region 18 of the head.

As best shown in FIG. 11, the reflected light beam is swept over atransverse beam dimension which is larger than the width of the bodyportion. Hence, here again, the field of view of the swept reflectedbeam is substantially independent of the barrel width.

Referring now to FIGS. 12 through 14, reference numeral 160 generallyidentifies a gun-shaped, single-windowed, laser scanning head arrangedfor retro-reflective scanning. As before, to simplify the description,like parts previously described have been assigned the same numerals asbefore. The head 160 comprises a laser light source, e.g. a semiconducorlaser diode 162, operative for generating a laser light beam, and fordirecting the same through an optical train including the positive lens164 and the light-reflecting mirror 166 adjustably mounted on a bendablebracket 168 which is, in turn, mounted on an optical bench 170. Themirror 166 is positioned in the light path of the incident beam todirect the same from the lens 164 towards and through an aperture 172centrally formed in the sensor mirror 174. The incident beam travelsunobstructedly through the aperture 172 and impinges on the scanningmirror 44 of the scanner mirror 46. The scanning mirror 44 directs theincident beam through the raised rear light-transmissive window 176 andout over an intermediate body region 20 and the front region 16 of thehead. The motor 46 is operative to sweep the incident beam over atransverse beam dimension which, in variance with the previousembodiments, is less than the width of the barrel 14. The exteriortransmission of the swept incident beam causes the transverse beam sweepdimension to be substantially independent of the barrel width. The lackof a direct relationship between the size of the swept incident beam andthe barrel width includes the possibility that the transverse beam sweepdimension may be greater or smaller than the barrel width. Of course, ifdesired, the incident beam may be swept over a field of view larger thanthe barrel width.

Likewise, the reflected beam travels outside of and past the front andintermediate body regions and passes through the same raised rear window176 for impingement on the scanning mirror 44.

The scanner motor 44 also sweeps the field of view of the reflected beamover a transverse beam sweep dimension which is less, but which could begreater, than the barrel width. The sensor mirror 174 is positioned inthe light path of the reflected beam such that the light-reflectingportions of the mirror 174 bounding the aperture 172 reflect thereflected beam rearwardly towards the sensor convex lens 180 and, inturn, to the light sensor element 182. The lens 180 and the sensorelement 182 are both mounted on respective brackets 184, 186 on theoptical bench 170.

It will be noted that only a single raised rear window 176 is mounted onthe head 160. No front window is necessary as in previous embodiments ofthe heads 10, 100, 130. Both the incident and reflected beams are sweptand travel through the same raised rear window 176. Here again, thefields of view of both the swept incident and reflected beams aresubstantially independent of the barrel width.

Turning now to the field-replaceable laser tube arrangement shown inFIG. 15, this arrangement can be used to quickly and easily replace thepreviously mentioned laser tube 22 mounted in a laser-scanning head. Asdescribed earlier, the tube 22 has an output end 23 and a non-output end25. The optical bench 24 has an enlarged recess 35 concentric with abore 25. An electrically conductive metal washer 36 is mounted in thebase of the recess 35. A metal cylindrical support sleeve 34 closelysurrounds the tube, and the diameter of the sleeve closely matches thediameter of recess 35. The output end 23 has a machined cylindricalshoulder 23a which is known to be concentric with the output laser beam.The diameter of shoulder 23a closely matches the diameter of bore 25.The shoulder 23a makes an electromechanical, non-soldered contact withthe washer 36. A high voltage power wire 200 extends through atransverse bore in the bench 24, and is soldered to the washer 36.

At the non-output end 25, a machined shoulder 25a is surrounded andengaged in force-transmitting, electrically-conductive relationshp withone end of a biasing means, i.e. elongated coiled spring 202. The otherend of spring 202 engages a removable electrically-conductive lockingcap 204 which is, in turn, detachably mounted on a stationary supportwall 206 of the head. A ground wire 208 is soldered to the cap 204.

When installed as shown in FIG. 15, the spring 202 is under compression,and is operative to constantly urge the tube 22 forwardly so as to biasthe machined shoulder 23a into affirmative electro-mechanical contactwith the washer 36. It should be noted that the spring 202 is thefunctional equivalent of the taut wire 38 described in connection withthe embodiment of FIGS. 1-6.

In order to replace a used tube with a fresh one, the removable cap 204is detached from the wall 206, thereby permitting the tensioned spring202 to be removed. The used tube 22 can now be slid out of the sleeve34, and the fresh tube inserted. The spring is then re-mounted on thenon-output end 25, and the cap is replaced to the illustrated position.

It will be noted that no soldering or unsoldering operations arerequired to remove the used tube or to install a fresh tube. The powerwires 200, 208 are not connected to the tube ends, but instead arepermanently connected to the components 36, 204. As noted above, this isin contrast to prior art laser tube-based scanning head, where the powerwires are directly connected to the tube ends.

It will further be noted that the laser tube 22, once installed, isautomatically optically aligned with the optic means, e.g. convex lens210. Hence, in contrast to prior art heads, no skilled personnel arerequired to align the output beam to the optic means.

The presence of a convex lens 210, rather than a concave lens,immediately at the output end of the laser tube 22 represents yetanother significant breakthrough in the art of laser scanning headsbecause, as will be demonstrated in connection with FIGS. 16 and 17, thepresent invention also includes a novel laser tube having a diverging,rather than the usual collimated, beam, as well as a method of makingsuch a laser tube.

Before discussing FIGS. 16 and 17, it should be noted that in many typesof lasers, a concave mirror is placed at one end region within the tube,and a substantially flat or plano-type mirror is placed within the tubeat its opposite end region. It is well known that the wave-fronts at themirror are the same shape as the latter, and that the wave-fronts areflat at a beam waist. Hence, the wave-front at the flat mirror islikewise flat, and there is a beam waist there. The wave-front at theconcave mirror is likewise concave. Typically, the inner surface of theflat mirror is coated with a coating which has a high predeterminedreflectivity, e.g. on the order of 100% maximum reflectivity, so thatideally, no transmission, except for unavoidable leakage, occurs throughthe flat mirror. Also, the inner surface of the concave mirror istypically coated with a coating having a reflectivity less than saidhigh predetermined reflectivity, e.g. on the order of 99% reflectivity,so that about 1% of the beam is transmitted through the concave mirror.Hence, the output end of the tube is located adjacent the concavemirror.

However, in the prior art lasers, the outer surface of the concavemirror is ground to just the right radius of curvature so as to flattenthe wave-fronts at the concave mirror in order to produce a flatwave-front and another beam waist at the ground outer surface of theconcave mirror. The beam waist at the concave mirror has a largerdiameter than at any other point within the laser between the mirrors,and is much greater than the beam waist at the flat mirror. In the fieldof laser scanners, the larger output beam at the concave mirror is verydesirable, because it provides the smallest beam divergence. Hence, inthis field, the output laser beam is always collimated, i.e.substantially parallel, and is always taken from the end adjacent thecorrected concave mirror.

In contrast, the present invention proposes modifying the laser tube sothat the output beam diverges. In one embodiment, the diverging outputbeam is taken from the end adjacent the concave mirror. In anotherembodiment, the diverging output beam is taken from the end adjacent theflat mirror.

Referring now to FIG. 16, the tube 22 has a flat mirror 212 adjacentnon-output end 25, and a concave mirror 214 adjacent output end 23. Theinner surface of flat mirror 212 has a coating 216 with the highpredetermined reflectively characteristic described above. The innersurface of concave mirror 214 has a coating 218 with the lowerreflectivity characteristics described above. The inner coated surfacesof the mirrors face each other. In accordance with one aspect of thisinvention, the outer surface 220 of the concave mirror 214 is ground tohave a curvature which is weak, optically speaking, in order to increasethe already divergent characteristic of the concave mirror. In apreferred embodiment, the outer surface is ground to provide an angle ofdivergence in the range of about 10 to about 100 milliradians.

Referring now to FIG. 17, like parts have been assigned like referencenumerals. It should be noted that the coatings on the mirrors have beenreversed such that the higher reflectivity coating 218 is now providedon the inner surface of the flat mirror 212, whereas the lowerreflectivity coating 216 is now provided at the inner surface of theconcave mirror 214. Since the light beam passing through the flat mirror212 is smallest at the latter, the far-field divergence of the beam isas large as possible due to the diffraction effect. The angle ofdivergence achieved by relying solely on the diffraction effect is onthe order of 3 milliradians, which is not useful in all scanner headapplications. Hence, in order to increase the angle of divergence, theouter surface 222 of the flat mirror 212 is ground to have a curvaturesuch as to diverge the beam to the required extent. The divergent outputbeam is emitted through the output end 23 adjacent the flat mirror 212.

In both cases, the modified laser beam diverges. It will be recalledthat in the typical optical system used in the laser scanning head, anegative lens is used to diverge the beam, and a positive lens is usedto focus the beam to the spot size and location desired. With thedivergent laser output of this invention, the negative lens and itsattendant size, weight and cost are eliminated. Returning then to FIG.15, it will be noted that the negative lens has been totally eliminated,and only the positive lens 210 is located adjacent the output end 23 ofthe tube.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

For example, the trigger switches 76, 76' respectively shown in FIGS. 1and 8 are both operative to depress the spring 78; however, switch 76 isprovided with a safety overload feature. A groove 75 is formed at therear of the trigger 76 and forms a user-engaging trigger portion 77 anda switch-actuating trigger portion 79. A guide finger 71 on the triggerextends into a guide aperture formed in a front abutment portion 73 onthe handle 12. In use, a user depresses the user-engaging portion 77,and causes the switch-actuating portion 79 to pivot and depress thespring 78. However, in the event that the user depresses theuser-engaging portion 77 too forcefully, i.e. beyond a predeterminedsafety load limit, the user-engaging portion 77 will slightly bend orflex relative to the switch-actuating portion 79 due to the slightstructural weakness caused by the presence of the groove 75. Thisfeature safeguards the spring 78 and the circuit board on which thespring 78 is mounted, and protects the spring 78 and its circuit boardfrom being damaged due to an excessive load on the trigger switch. Thepredetermined safety load limit for the trigger is determinedbeforehand, and the user-engaging portion 77 only flexes if this limitis exceeded. As a further safety feature, the user-engaging portion 77is permitted to flex only until the latter abuts against the frontabutment portion 73 which effectivley prevents any further rearwardmovement of the trigger.

Another useful construction relates to increasing the depth of field,i.e. the working distance, of the laser scanning head. It will berecalled that a bar code symbol can be read at either side of thereference plane, and the range in which the symbol is read is defined asthe depth of field. For convenience, a symbol that is located betweenthe reference plane and the head is defined as a "close-in" symbol,whereas a symbol that is located on the other side of the referenceplane away from the head is defined as a "far-out" symbol.

As noted above, the sensor means detects the light intensity of thereflected light beam, and generates an electrical signal indicative ofthe detected light intensity. This electrical signal is then processedby the signal processing means. Inasmuch as the amplitude of thereflected light, and hence the amplitude of the generated electricalsignal, is a function of the distance at which the symbol is locatedrelative to the sensor means in the head, laser scanning system designsshould take into account the variation in amplitude which occurs forclose-in and far-out symbols. For example, in a case where the depth offield ranges from about 1/2" to about 6", and where the reference planeis on the order of 4" from the sensor means, then the amplitudevariation at the opposite ends of the range can be on the order of100:1. This amplitude variation is undesirably high, but could beelectrically compensated for in the electronic signal processingcircuitry. However, the required electronic circuitry is highly complexand expensive, thereby relegating the laser scanning system designer tobe satisfied with a much smaller depth of field, rather than include thecomplex electronic circuitry.

In accordance with the invention, passive optical means are provided fordecreasing the aforementioned amplitude variation, particularly byreducing the amplitude associated with a close-in symbol without theaddition of the complex electronics. In a preferred embodiment, theaforementioned window associated with the sensor means, i.e. non-scanwindow 52 or scan windows 150, 176, rather than constituting a merewindow with no light-modifying properties, may be replaced by a positivelens such as a fresnel lens. The fresnel lens window has a height largerthan that of the sensor means, i.e. the photo-detectors. For far-outsymbols, the fresnel lens window directs virtually all the returningrays of the reflected light beam to the photo-detectors. This boosts thesignal strength associated with the far-out symbol. For close-insymbols, only a portion of the returning rays of the reflected lightbeam is focused by the fresnel lens window on the photo-detectors,thereby decreasing the signal strength associated with the close-insymbol.

Hence, the fresnel lens window is optically operative not only to reducethe amplitude associated with a close-in symbol, but also to increasethe amplitude associated with a far-out symbol. In the aforementionedcase where the depth of field ranges from about 1/2" to about 6" fromthe sensor means, the fresnel lens window changes the amplitudevariation from about 100:1 to about 5:1. This reduced dynamic range iswell within the capabilities of the electronics of the signal processingmeans, which now need not be designed with complex electronic signalprocessing circuitry to account for high amplitude variation. The depthof field has been increased without the need for such additional complexelectronic circuitry.

Rather than a fresnel lens window, another passive opticallight-modifier means such as a stationary louver configurated like avenetian blind with mutually parallel permanently-open slats could bemounted at the front region of the housing, either forwardly orrearwardly of the window associated with the sensor means. The closerthe symbol is to the sensor means, the more light is blocked by thelouver. When the symbol is distant, more light will pass through thelouver to the sensor means. Alternatively, an overhead visor or shadecould be mounted forwardly of the sensor means. As the symbol comescloser to the sensor means, the visor blocks more and more light fromthe sensor means. In both cases, the reflected light beam is opticallymodified and the amplitude associated with close-in symbols will bereduced, thereby flattening the amplitude variation and increasing thedepth of field.

Still another way of optically increasing the depth of field bydecreasing the amplitude variation is to constitute the windowassociated with the sensor means as a narrow spectral band interferencefilter (6328Å), or to mount a discrete interference filter at eitherside of the window. The filter is operative to suppress ambient lightand to attenuate the amplitude associated with close-in symbols, therebyenhancing the dynamic range.

Yet another way of optically increasing the depth of field by decreasingthe amplitude variation is to mount the sensor means at the rear regionof the housing. As shown in FIGS. 9 and 10, the sensor means 140 islocated at the rear of the housing, and the amplitude variation forfar-out and close-in symbols for the aforementioned case where the depthof field is desired to range from about 1/2" to about 6" is reduced fromabout 100:1 to about 4:1 without the necessity of providing for afresnel lens window or complex signal processing circuitry.

The retro-reflective embodiment of FIGS. 12-14 is highly advantageous onthe matter of signal to noise ratio, and this embodiment together withthe increased depth of field feature described above constitute a veryefficient laser scanning head.

Another advantageous feature relating to increasing the signal to noiseratio lies in synchronous detection. The laser diodes 102 (FIG. 8) and162 (FIG. 13) and the light source elements 132a, 132b (FIG. 11) arewell suited to be pulsed at some predetermined frequency, and the sensormeans includes narrowband amplifiers tuned to said pulsed frequency.Hence, the signal to noise ratio is greatly increased.

While the invention has been illustrated and described as embodied in anarrow-bodied, single-and twin-windowed, portable laser scanning headfor reading bar code symbols, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A field-replaceable laser tubearrangement for a laser scanning head of a laser scanning system forreading bar code symbols, said arrangment comprising:(a) a laser tubefor emitting a laser beam; (b) optic means for directing the emittedlaser beam towards the bar code symbol to be read; and (c) means formounting the laser tube in a non-soldered relationship with the head andin an automatically optically-aligned relationship with the optic meansto permit quick and easy tube replacement for field maintenance.
 2. Thearrangement as defined in claim 1, wherein the laser tube has an outputend and a non-output end, and wherein the tube-mounting means includes abore concentric with the output end for receiving the latter inoptically-aligned relationship, and wherein the tube-mounting meansincludes an electrically conductive element in electromechanicalnon-soldered contact with the output end of the tube, and biasing meansat the non-output end and in non-soldered contact therewith, for urgingthe output end of the tube into affirmative electromechanical contactwith the electrically conductive element.
 3. In a scanning system forreading bar code symbols of the type including actuatable components fordirecting an incident light beam towards a bar code symbol forreflection therefrom, for detecting the light intensity of the reflectedlight, and for processing the detected light intensity into datadescriptive of the symbol, a scanning head comprising:(a) trigger meansincluding a depressable element fixedly mounted on the head andelectrically connected to the actuatable components, and a user-operatedmovable trigger element mounted on the head for movement relative to thedepressable element along a trigger path for depressing the depressableelement to actuate the components and initiate symbol reading; and (b)safety overload means associated with the movable trigger element, andoperative for preventing the latter from depressing the depressableelement with a force exceeding a predetermined safety limit so as toprevent damage to the depressable element in the event that the usermoves the trigger element with a force exceeding the safety limit. 4.The head as defined in claim 3, wherein the trigger element includes auser-engaging portion and an actuating portion operatively connected tothe latter for joint movement during one portion of the trigger path,and wherein the safety overload means includes means in the triggerelement of causing the user-engaging portion to move relative to theactuating portion during another portion of the tirgger path when theuser has moved the trigger element with a force exceeding the safetylimit.
 5. In a scanning head for reading bar code symbols of the typeincluding light source means for generating an incident light beam,optical means for directing the incident beam towards a bar code symbolfor reflection therefrom to generate reflected light, and scanning meansfor scanning the bar code symbol, a support structure comprising:alight-weight, one-piece plastic support bench for supporting the lightsource means, the optic means and the scanning means within the head,said bench being fabricated by mass-production techniques.
 6. Thesupport structure as defined in claim 5, wherein the bench isconstituted of a moldable plastic material.
 7. A method of fabricating asupport structure for supporting a light source means, an optic meansand a scanning means within a scanning head for reading bar codesymbols, said method comprising the steps of:forming a light-weightsupport bench of one-piece plastic construction by mass-productiontechniques.
 8. The method as defined in claim 7, wherein said formingstep is performed by molding the bench.
 9. A support structure for usein a scanning head of the type having a light source means forgenerating a light beam, optic means for directing the light beam towardan object to be scanned, and scanning means for scanning the object,said support structure comprising:a light-weight support for separatelypositionably supporting each one of the light source means, the opticmeans and the scanning means at predetermined optically-preciselocations relative to one another in an operative optically-alignedassembly, said support being operative for separately re-positionablysupporting each one of the light source means, the optic means and thescanning means at said optically-precise locations and in saidoptically-aligned assembly for field replacement.
 10. The supportstructure as defined in claim 9, wherein the light source means includesa gas laser tube for emitting a laser light beam.
 11. The supportstructure as defined in claim 9, wherein the light source means includesa semiconductor laser diode for emitting a laser light beam.
 12. Thesupport structure as defined in claim 9; and further comprising shockmounts on the support for shock mounting the light source means, theoptic means and the scanning means within the head.